How to Prove a Trigonometric Identity Involving x, y, and z?

[skcollins]

If xy+yz+zx=1 then prove (x^2-1)(y^2-1)/xy+(y^2-1)(z^2-1)/yz+(z^2-1)(x^2-1)/zx=4 with trigonometric identities such as cotAcotB+cotBcotC+cotCcotA=1

 

[Greg]

Hello skcollins and welcome to MHB! :D

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